1. Field of the Invention
The present invention relates to a document transport device, and specifically relates to a document transport device provided with a discharge tray to receive ejected documents and disposed below a document feed tray (document tray) accommodating stacked documents.
2. Description of the Related Art
Document transport devices have been proposed which can be installed in a narrow space by arranging a feed tray and a discharge tray one above another in a vertical direction so as to avoid having the feed tray extend beyond the side of the device. In such document transport devices, a document in the feed tray passes through a first U-turn and is inverted and placed on a document table, and after predetermined processing such as optical exposure on said document table and the like, said document is transported in the same direction as during the initial feeding and passes through a second U-turn and is inverted and ejected to a discharge tray at a position below said feed tray.
The aforesaid document transport device is disadvantageous inasmuch as the feed tray and the discharge tray are arranged one over another in a vertical direction such that the majority of the discharge tray is covered and concealed by the feed tray, making it difficult to manually remove documents stacked on the discharge tray. This difficulty is magnified particularly in the case of small size documents. Therefore, consideration has been given to facilitate easy removal of documents by exposing part of the discharge tray (i.e., the part from the second U-turn) by shortening the length of the feed tray in the document transport direction. Simply shortening the length of the feed tray, however, produces another disadvantage inasmuch as large size documents cannot be stacked on the feed tray.
Accordingly, it has been proposed to construct a feed tray capable of being folded at a predetermined part (e.g., the center part) in the document transport direction, such that small size documents are exposed on the discharge tray by folding up the aforesaid folding part of the feed tray to allow easy document removal, and large size documents can be accommodated on the feed tray by opening the aforesaid folding part of the feed tray. It has further been proposed to construct a feed tray comprising a main tray wherein the edge on the leading edge side is connected to the entrance to the aforesaid first U-turn path, and an auxiliary tray is mounted on the edge of said main tray on the trailing edge side and is foldable so as to be overlaid on the top surface of said main tray. In this instance, "leading edge" refers to the direction of document transport, and "trailing edge" refers to the opposite direction.
From the perspective of operational characteristics when placing a document as well as preventing an increase in the size of the document transport device, there is a tendency to construct a thin feed tray. It is therefore difficult to form sufficient concavoconvexity of the surface of the feed tray, which results in difficulty manually removing document placed on the feed tray when said documents are of a size that is smaller than the feed tray. Although consideration has been given to dividing the feed tray into a plurality of foldable parts to eliminate this disadvantage, such an arrangement not only complicates the mechanism of the auxiliary tray, but also produces a further disadvantage of complicating the operation of opening and closing the auxiliary tray.
When a feed tray comprises a main tray and an auxiliary tray capable of folding as previously described, a height differential and gap are produced on the back surface (bottom surface) of the folding part, such that the leading edge of a sheet passing through said second U-turn path and discharged to the discharge tray becomes caught by the height differential or gap so as to be bent or damaged. Furthermore, when such bending causes disruption of the document on the discharge tray, problems such as jamming of a subsequently discharged document readily occur. A further disadvantage is the particularly common occurrence of upward curling of the edges of a document on the tray when a document is discharged onto the discharge tray.